Bug Report: Drop Shadow Node causes Glitches in Renders

Natron RB-2.3 at version e8d25fb
Ubuntu18.04 Linux, AMD Threadripper, Nvidia

When using the DropShadow node, some frames render with glitched shadows.

See here a correct rendered pic:

and here the next frame which rendered with glitched shadow:

Scene setup:

Does the same frame look ok in the viewer (if not what if you refresh)? Does the same frame look ok if rendered manually (only render that frame)?

In the viewer it looks correct and also when rendering this frame manually it comes without glitches.

Just tested with newest build (RC15), issues is still present.
Workaround is rerendering the frames with the wrong DropShadow, since the glitch is not in DiskCache.

The bug is most likely a threading issue, I have experienced similar issues in the past.

Just figured out that the glitched DropShadow is sometimes even cached in the DiskCache and when you rerender its still glitched…

However, would be nice to get this fixed somehow…
Natron still has amazing render speeds on multicore computers.

So, is the issue only with DropShadow? Do you get the same issues with other PyPlugs, or OFX? If you create a new project with a solid (or whatever) and DropShadow, do you get the same issue? I’m looking for something that can easily be replicated.

Currently only using DropShadow FX, will report as soon as I figured out more and could reproduce it in a simple comp…

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